The Evolved UMTS Terrestrial Radio Access Network (E-UTRAN), standardized by members of the 3rd Generation Partnership Project (3GPP), includes base stations called enhanced NodeBs (eNBs or eNodeBs), providing the E-UTRA user plane and control plane protocol terminations towards the UE. The eNBs are interconnected with each other using the X2 interface. The eNBs are also connected using the S1 interface to the EPC (Evolved Packet Core), more specifically to the MME (Mobility Management Entity) by means of the S1-MME interface and to the Serving Gateway (S-GW) by means of the S1-U interface. The S1 interface supports many-to-many relation between MMEs/S-GWs and eNBs. A simplified view of the E-UTRAN architecture is provided by FIGS. 1 and 2.
The eNB 110 hosts functionalities such as Radio Resource Management (RRM), radio bearer control, admission control, header compression of user plane data towards serving gateway, and/or routing of user plane data towards the serving gateway. The MME 120 is the control node that processes the signaling between the UE and the CN (core network). Significant functions of the MME 120 are related to connection management and bearer management, which are handled via Non Access Stratum (NAS) protocols. The S-GW 130 is the anchor point for UE mobility, and also includes other functionalities such as temporary DL (down link) data buffering while the UE is being paged, packet routing and forwarding to the right eNB, and/or gathering of information for charging and lawful interception. The PDN Gateway 140 (P-GW, not shown in FIG. 1) is the node responsible for UE IP address allocation, as well as Quality of Service (QoS) enforcement (as further discussed below). The reader is referred to 3GPP TS 36.300 and the references therein for further details of functionalities of the different nodes.
FIG. 2 gives a summary of the functionalities of the different nodes. The reader is referred to the 3GPP document “Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall Description; Stage 2,” 3GPP TS 36.300, v. 11.3.0 (September 2012), available at www.3gpp.org, and the references therein for the details of the functionalities of the different nodes. In FIG. 2, the boxes labeled eNB 110, MME 120, S-GW 130, and P-GW 140 depict the logical nodes, which may correspond to separate and distinct physical units, in some cases. The smaller boxes within the larger boxes depict the functional entities of the control plane. The shaded boxes within the box labeled eNB 110 depict the radio protocol layers.
The wireless local-area network (WLAN) technology known as “Wi-Fi” has been standardized by IEEE in the 802.11 series of specifications (i.e., as “IEEE Standard for Information technology-Telecommunications and information exchange between systems. Local and metropolitan area networks-Specific requirements. Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications”).
Using Wi-Fi/WLAN (the two terms are used interchangeably throughout this document) to offload traffic from the mobile networks is becoming more and more interesting from both the operators' and end users' points of view. Reasons for this include the additional frequency that may be obtained—by using Wi-Fi, operators can access an additional 85 MHz of radio bandwidth in the 2.4 GHz band and nearly another 500 MHz in the 5 GHz band. Cost is another factor, as Wi-Fi uses unlicensed frequency that is free of charge. On top of that, the cost of a typical Wi-Fi Access Points (AP), from both capital expense (CAPEX) and operational expense (OPEX) perspectives, is considerably lower than that of a 3GPP base station (BS/eNB).
In addition, operators can take advantage of already deployed APs that are already deployed in hotspots such as train stations, airports, stadiums, shopping malls, etc. Further, most end users are also currently accustomed to having Wi-Fi for “free” at home (as home broadband subscriptions are usually flat rate) and at many public places. Another factor is the high data rates that are increasingly demanded by customers. Under low interference conditions and assuming the user is close to the Wi-Fi AP, Wi-Fi can provide peak data rates that outshine that of current mobile networks (for example, theoretically up to 600 Mbps for IEEE 802.11n deployments with MIMO (Multiple Input Multiple Output)).
Still another factor in this increased interest in Wi-Fi integration, or at least in closer cooperation between WLANs and cellular networks, is the rapidly increasing support for Wi-Fi among cellular telephones. Many portable devices currently available in the market, including virtually all smartphones, support Wi-Fi. Note that in the specifications that define the Wi-Fi world, the term “station” (STA) is used instead of UE; because this document is generally considered with devices that support both a cellular technology (such as E-UTRA) and Wi-Fi, the terms UE, STA and terminal are used interchangeably in this document.
A very simplified Wi-Fi architecture is illustrated in FIG. 3 and FIG. 4, below. On the user plane, illustrated in FIG. 3, a very lean architecture is employed, where the UE/STA is connected to the Wi-Fi Access Point (AP). The Wi-Fi in turn can be directly connected to the Internet, thus providing the UE/STA access to application servers on the Internet. In the control plane, as illustrated in FIG. 4, an Access point Controller (AC) may handle the management of the AP. One AC usually handles the management of several APs. Security/authentication of users can be handled via an Authentication, Authorization and Accounting (AAA) entity, which is shown as a RADIUS server in FIG. 4. Remote Administration Dial-In User Service (RADIUS) is the most widely used network protocol for providing a centralized AAA management (RFC 2865).
The Access Network Discovery and Selection Function (ANDFS) is an entity defined by 3GPP for providing access discovery information as well as mobility and routing policies to the UE. ANDFS is a new entity added to the 3GPP architecture in Release 8 of 3GPP TS 23.402. (See “Architecture Enhancements for non-3GPP Accesses,” 3GPP TS 23.402, v. 11.4.0 (September 2012), available at www.3gpp.org.) A simplified ANDSF architecture is depicted in FIG. 5. As shown in the figure, the ANDSF server is connected to the UE, and its main goal is to provide the UE with access network information in a resource efficient and secure manner. The communication between the UE and the ANDSF server is defined as an IP-based interface referred to as the S14 interface.
By supplying information about both available 3GPP and non-3GPP access networks to the UE, the ANDSF enables an energy-efficient mechanism of network discovery, where the UE can avoid continuous and energy-consuming background scanning. Furthermore, ANDSF provides the mobile operators with a tool for the implementation of flexible and efficient UE steering of access mechanisms, where policy control can guide UEs to select one particular RAN over another.
The ANDSF supplies three types of information—discovery information, inter-system mobility policies (ISMP) and inter-system routing policies (ISRP). All these are summarized and implemented via ANDSF managed objects (MO), which are communicated to the UEs via an over-the-top (OTT) signaling channel, as SOAP-XML messages.
The discovery information provides the UE with information regarding the availability of different RATs in the UE's vicinity. This helps the UE to discover available access networks, including 3GPP and non-3GPP access networks, without the burden of continuous background scanning. Inter-System Mobility Policies (ISMP) are policies which guide the UE to select the most preferable 3GPP or non-3GPP access. The ISMP are used for UEs that access a single access network (e.g., 3GPP or Wi-Fi) at a time.
The ISMP information specifies the behavior of UEs that can be connected to only one access network at a given time (either 3GPP, WLAN, WiMAX, etc.). If the UE, however, supports connection to several access networks at the same time, the operator can use the third type of information, ISRP, to increase the granularity of the RAN selection. In that case, the UEs will be provided with policies that specify how the traffic flows should be distributed over the different RAN. For example, voice might be only allowed to be carried over a 3GPP RAN connection, while Internet video streaming and best-effort traffic can be routed via WLAN. The ANDSF provides mobile operators with a tool to determine how the UEs connect to different RANs, and hence allows them to add more flexibility in their traffic planning.
As noted above, because of the proliferation of devices that have both Wi-Fi and 3GPP mobile broadband support, offloading traffic to the Wi-Fi network is becoming very interesting, both from the user's and the operator's perspectives. The main difference between traffic steering to and from Wi-Fi, as compared to steering between 3GPP networks or 3GPP-“friendly” networks such as CDMA2000 networks, is that it is generally the terminal that decides when it shall select a Wi-Fi Access Point (AP), while in wide-area networks it is the network that is in charge of the network access decisions.
For technical and historical reasons, the Wi-Fi deployment scenario is in many cases fundamentally different than the cellular deployment. For this reason, special considerations have to be made when integrating Wi-Fi to 3GPP networks. For example, with currently existing technologies the information regarding a wireless terminal's communication in one wireless network, such as a Wi-Fi, is not readily available in another wireless network. This can be especially problematic if one wireless network is controlling the wireless terminal's communication in the other wireless network. International Patent Application Publication WO 2014/084792 A1 describes a method in a mobile terminal in which the terminal transmits information to a first wireless network of the mobile terminal's connection status with respect to a second wireless network. The techniques described herein thus focus on several aspects of integrating Wi-Fi to 3GPP networks, including the problem addressed by the WO 2014/084792 A1 publication, to realize optimal steering of traffic while considering both the end user's as well as the network's performance.